Heads up displays (HUD's) have been well known for many years, and are used or are being considered for use in many applications including medical, scientific data visualization, aircraft, automobiles, boats, large farm equipment, and heavy-duty construction equipment. In a vehicular application, the driver can see the HUD in the field of view along with the road ahead and real objects on or near the road. Thus, using a HUD, an automobile driver can see the instrument panel superimposed on road without having to glance away to the display, focus on the display and then having to look back and refocus to the road. This saves eye-strain and improves driver performance.
Existing heads up displays create an image that is projected into the field of view of a user so that the user can glance at the projected image whenever the information contained in the image is needed. The existing systems typically use lenses that direct an image towards a partially transparent surface through which the user views the scene, so that the user sees both the scene and the virtual image that appears to be located on the other side of the partially transparent surface. Many existing systems use broadband light and require very expensive lens assemblies to form color corrected images. Holographic systems are an inexpensive solution to the color correction problem, but they can introduce image blurring due to bandwidth generated problems. Additionally, the bandwidth of the light source limits the perceived depth of the image, with a wide bandwidth light source requiring the image to be placed close to the observer to minimize image distortions and blur. Consequently, users must still change their focus whenever they wish to view the projected image. The need to change one's focus from a distant object to a nearby object takes time, typically several tens of milliseconds (or longer for older people, viz., people with presbyopia). Such delays can constitute a significant safety issue, especially in situations where events occur very rapidly, e.g. in automobiles and aircraft, as well as in situations where the shear size and scale of the applications can put others at risk very quickly in spite of relatively slow moving equipment, e.g. equipment in construction zones and boats). What is needed is a way to seamlessly integrate the display into the scene at a distance comparable to the distance of the scene.
In addition, existing systems are expensive, often requiring lenses that cost thousands of dollars. For example, the Sim Eye XL100A from Rockwell Collins costs $87,500 each.1 
1http://www.keo.com/SIMEYE100A.htm 
Heads up displays can be categorized into low information content displays and high information content displays. Low information content displays include, for example, on/off indicators and turn signal indicators. High information content displays include, for example, text using 12 point font, video images and the like. The bulk of existing systems and publications and patents were developed for low information content systems because the technology for high information content systems has not been sufficiently developed for field use. The difference between high and low information content displays is significant because high information content displays require high resolution that is not feasible in low information content systems. Low information content systems do not require high resolution, therefore do not require a low bandwidth illumination source and hence can be inexpensive.
In addition, HUDs can also be categorized as being fixed HUDs or as mobile HUDs. Fixed HUDs are mounted to a structural member, and the user is positioned, for example, in a seat that affords the user a view of the image formed using the HUD. An example of a mobile HUD is a helmet mounted HUD. Another example is eye-wear that includes display optics that allow a user to view, for example, a computer monitor as an image projected in front of the user.
A closely related technology is virtual reality (VR) technology, which can be categorized as 100% VR where everything seen by the user is created and nothing viewed by the user is “real”. Applications include simulators and video games. A related VR technology is augmented virtual reality (AVR), where information is projected into the field of view that is derived in part from local information content. This invention more specifically relates to AVR, but it should be apparent that it can also be used in VR applications.
U.S. Pat. No. 4,457,579 describes an arrangement for reducing influence of diffuse and direct reflections in a display device based on a light source emitting in a narrow band said display device comprising an absorption filter having a pass band enclosing the center frequency of the light source said absorption filter being placed in the beam path between the light source and the observer and immediately adjacent reflecting means, the bandwidth of the filter being wider than the bandwidth of the light source, but considerably narrower than the spectral bandwidth of the eye.
U.S. Pat. No. 5,576,886 describes an aircraft head-up display with a combiner using a thin film dielectric reflector with a contoured reflectance spectrum of a narrow bandwidth that matches the spectrum of the light output of a cathode-ray tube whose phosphors produce a narrow bandwidth light output used to create visual data for display to the pilot. The dielectric combiner is constructed with a dielectric coating made up of ion deposited layers, with alternate layers having different indices of refraction and possibly different thicknesses near one quarter wavelength thick. The resultant combiner transmits ambient light essentially without attenuation at all visible light frequencies except those frequencies of the visual data produced by the CRT phosphors, which are reflected into superposition with the background viewable through the combiner.
U.S. Pat. No. 4,447,128 describes a diffraction grating head up display is disclosed which blocks solar radiation from impinging upon and washing out the image of display information on an optical display device. This is accomplished by means of a filter such an optical element made of photochromic material which is positioned between the display information surface and relay optics lenses, preferably at the back focal plane thereof, so that focused solar radiation darkens a localized spot in the photochromic material. The darkened spot blocks the solar energy but reversibly lightens after the focused solar energy is removed. This photochromic material allows substantially unimpeded transmittance of the image of the display information except at the darkened spot. Also included in the optical system are a folding reflector and a combiner lens element which combines and superimposes the image of the display information on the scene being viewed when an observer looks through the combiner element. This combiner element is a diffraction grating holographic lens which is reflective or diffractive of a narrow bandwidth of light which includes the narrow bandwidth light of the display information.
U.S. Pat. No. 4,930,847 describes a method for producing multicolor holographic optical elements useful in presentation of multicolor holographic images in a head-up display (HUD) system. Because of restricted geometries, such HUDs should allow for reconstruction of wavefronts employing all readout beams coming from the same direction, with the reconstructed wavefront being cast in a specified direction. A first method for producing a multicolor HOE satisfying these conditions makes all recording at the same wavelength but with varying record geometries. A second method for producing multicolor HOEs employs the same record geometries but uses varying wavelengths of recording light. This allows the recording to be made under conditions where the diffraction efficiency of the resulting HOEs is controlled, as are the displayed colors. As the consequence of this, the multicolor HOE can be made under conditions which allow the Bragg condition to be satisfied for each of the readout wavelengths allowing a uniformly bright multicolor wavefront to be reconstructed. A third method for producing such HOEs is to further change the recording geometry by redirecting all the recording wavefronts through the same angular interval. This minimizes the crosstalk which occurs between images recorded at different wavelengths. Also disclosed are apparatus for display of each of the HOEs.
U.S. Pat. No. 4,218,111 describes an integrated optical design of head-up displays suitable for use in aircraft cockpits and the like. The display system is comprised of a holographic optical element used as the combiner for presenting a direct view of the exterior on which are superimposed image signals generated by a source device such as a cathode ray tube and transmitted to the combiner through an optical system including a relay lens containing tilted and decentered optical elements to compensate for the aberration present in the holographic optical element. It further describes four relay lens design forms particularly suited for use in the design of such holographic head-up displays. The disclosure includes integrated designs in which (a) the holographic element may or may not be constructed with aberrated wavefront and (b) a beam splitter is incorporated for insertion of a stand-by sight, possibly also being tilted for the correction of aberrations.
U.S. Pat. No. 6,175,431 describes a projection system and a method of displaying a projected input image on a projection screen of the system utilize one or more reconfigurable holographic optical elements (HOEs) to optically manipulate propagating light in the system. The reconfigurable HOEs may be configured to perform simple optical functions that are commonly associated with traditional optical devices, such as lenses, prisms and mirrors. However, the reconfigurable HOEs may also be configured to perform sophisticated optical manipulations, such as varying the light intensity toward a specific direction and generating virtual (holographic) images. Each reconfigurable HOE includes a hologram that is sandwiched between two electrode layers. The hologram is a holographic photopolymeric film that has been combined with liquid crystal. The hologram has an optical property that changes in response to an applied electrical field. The reconfigurable HOEs may be included in a color filter of the system to selectively diffract tristimulus color lights to a display panel in order to provide a color display of the input image that is projected onto the projection screen. The reconfigurable HOEs may also be included in a projection optics to magnify the projected image on the projection screen and/or redirect the projected image to form a tiled image on the projection screen. Furthermore, the reconfigurable HOEs may be used in the projection screen to vary the light intensity toward specific viewing positions. In one application, the reconfigurable HOEs in the projection screen allow the system to present the display image in a stereoscopic form.
Holographic combiners are also known in the literature. Wood, et al. discuss the practical aspects of forming holographic combiners.2 This paper focuses on image brightness, not depth of focus. Hurst et al. describe the use of holographic wedges in heads up displays.3 Smirnov et al. describe full color reflection type holographic screens, but focus on the hologram fabrication process.4 Blumenfeld and Amitai describe a heads up display using 3 lenses and a diffractive element.5 Ramsbottom, et al. describe the use of holography in automotive heads up applications, where images are formed in space near to the automobile.6 Bartlett describes the use of holographic optical elements in heads up displays, but uses a 15 nm spectral source, which is not sufficiently narrow to allow sharp images, and does not address the apparent distance of the image created by the heads up display.7 
2 R. B. Wood, M. A. Thomas, “Holographic head-up display combiners with optimal photometric efficiency and uniformity”, SPIE Vol. 1289 Cockpit Displays and Visual Simulation (1990) 
3A. E. Hurst, P. J. Rogers, “Use of holographic wedges in large field of view head-up displays”, SPIE Vol. 2404, pp. 286-292, 1995
4V. V. Smirnov, et al., “A full color reflection type holographic screen”, SPIE Vol. 3293, pp. 175-182, (1998) 
5Y. Blumenfeld, Y. Amitai, “Designing a head up display system with a hybrid diffractive-refractive lens”, SPIE Vol. 2426, pp. 366-372 (1995) 
6 A. Ramsbottom, S. Sergeant, D. Sheel, “Holography for automotive Head-up-displays”, SPIE Vol. 1667 Practical Holography, pp. 146-164, (1992) 
7C. T. Bartlett, “The head up display for the advanced cockpit”, SPIE Vol. 2219 Cockpit Displays, pp. 22-33 (1994) 
All the heads up displays are limited in resolution and the distance of the virtual image. Thus, a better system for providing heads up displays is needed for low cost, high resolution, and high information content, and this solution is provided by the following invention.